Check this site out. There is better for just innerHTML but I thought this one did a nice job of dealing with the browser issue.
http://www.xs4all.nl/~ppk/js/layerwrite.html
I agree do XML via server side XSLT. I just wasnt sure how it applied to changing page content without a page load. Actually re-reading your last two posts I think I am confused on what I am trying to help you with, and thus perhaps just confusing the issue with stuff you already know. If thats the case, sorry
Cul